基于交叉射流与切向旋流的CH_4柔和燃烧特性对比

轴向分级柔和燃烧器中,采用了交叉射流、切向旋流两种掺混方式,通过实验结合数值计算的方法,从流场和组分分布角度比较了两种掺混方式的掺混特点,从火焰特征、NO/CO排放方面比较了燃烧性能.实验以甲烷为燃料,热功率为16.2~25.9kW,相对切向旋流,交叉射流延缓了燃料、空气的直接混合,燃料、空气燃烧前经回流烟气充分预热和稀释,火焰根部有抬升,反应区体积大,火焰特征更接近柔和燃烧.同时,交叉射流分级燃烧器的污染物排放性能更优,回流比例为0.5、当量比为0.6时,烟气中NO和CO体积分数均仅为4×10-6.

Comparison of CH4 moderate or intense low-oxygen dilution combustion characteristics based on cross-flow jet mixing and swirl mixing

Two axially-staged moderate or intense low-oxygen dilution(MILD) configurations, based on cross-flow jet mixing and swirl mixing, were numerically and experimentally studied to compare their mixing performance from flow field pattern and species distribution, and to compare their combustion property from flame behavior and NO and CO emissions. The experiment fuel was methane and the heat load was regulated in the range of 16.2 to 25.9kW. The mixing between fuel and air stream is delayed in the cross-flow jet mixing configuration compared to the swirl mixing configuration, and thereby the recirculated hot flue gas preheats and diluts the fuel and air stream before spontaneous reaction in the former configuration. Compared to the swirl mixing configuration, higher flame lift-off height and more spatially distributed flame are observed in the cross-flow jet mixing configuration, of which flame behavior is also closer to MILD combustion. Furthermore, lower NO and CO emissions are observed for the cross-flow jet mixing staged combustor; at gas recirculation ratio of 0.5 and equivalence ratio of 0.6, the volume fractions of NO and CO in the flue gas are both 4×10^-6.